The present invention pertains to reconstituting lyophilized drugs for use, and more particularly to a needle assembly, kit, and method for preparing a quantity of a lyophilized drug in an injection pen cartridge for use.
Due to a short shelf life or other difficulties in storage or transport, many drugs, such as human growth hormone, are lyophilized or freeze-dried for storage and transported in a powdered state. These drugs must then be reconstituted with water or another diluent fluid before use. Typically, a quantity of the powdered drug is stored in a vial sealed with a needle penetrable stopper. When the drug is needed, the stopper is penetrated with a syringe needle and the reconstituting fluid is added to the vial for mixing with the powdered drug. Once the drug is prepared, the mixed fluid is withdrawn from the container and administered in desired doses.
However, with many such drugs the fluid stream should not be injected directly onto the powdered drug as direct application can cause foaming, spraying and/or incorrect mixing. Further, if the fluid is added without a corresponding release of gas pressure from the vial, the pressure inside the vial can increase, potentially interfering with the reconstituting effect, interfering with fluid flow or potentially damaging the vial or syringe. This can cause difficulty in removing the drug for administration. Additionally, sufficient pressure in the vial can result in the drug or liquid being blown past the needle in the stopper. This condition, known as “blowback,” can create inaccuracies in drug concentration and effective dosage.
One needle assembly for transferring liquid to or from a vial is suggested in U.S. Pat. No. 4,537,593 to Alchas. Alchas suggests a needle assembly beginning with a hub attachable to a syringe and terminating in a needle with a closed distal end having a protruding knife-blade with a width greater than the needle. A slot which serves as a side port is provided near the end of the needle through which liquid is introduced or withdrawn. In one form, a slidable sleeve is located between the needle hub and the protruding knife-blade. In use, Alchas suggests that the knife-blade should be pushed through the vial stopper, whereupon the stopper pushes the slidable sleeve upwards on the needle until it abuts the needle hub, and by continuing introduction of the needle, the sleeve then penetrates the stopper. In another form, the sleeve is fixed to the needle. After needle introduction, the liquid is then injected through the side slot into the vial, with air venting between the sleeve and needle during such liquid injection.
While functional, the Alchas design is not without its shortcomings. For one thing, the needle assembly, which is readily visible in use, may have a menacing appearance to some users. Moreover, as the needle assembly is suggested by Alchas to be used multiple times to transfer material to multiple containers, this use raises concerns of contamination of the drug or needle assembly during use. Still further, the knife-blade of the needle assembly may cause mechanical damage to a stopper which may compromise its ability to form an adequate seal.
One prior kit for reconstituting a drug in an injection pen cartridge is illustrated in FIGS. 1 and 2. In this kit, the needle of the syringe is inserted into a cartridge through an adapter, which forces the needle to be held at an angle to the cartridge wall, directing the diluent fluid at a wall of the cartridge. However, so injecting the diluent fluid may be more difficult or time-consuming than desired due to the need to displace gas in the cartridge with diluent. In particular, unless a user wiggles the syringe during the injection process to allow gas to escape from the cartridge through temporary passages between the needle and stopper, a user normally needs to press the syringe plunger rod to inject some diluent, allow gas to percolate from the cartridge through the injection needle and up to the syringe plunger, and then press or pump the plunger rod again, and repeat the process as needed, until the diluent is emptied from the syringe.
Consequently, it would be desirable to provide an apparatus and a method that overcomes these and other shortcomings of the prior art.